An academy which is battling to turn around its academic performance while tackling a £969,000 deficit is trying to change the terms of a private finance initiative (PFI) deal that cost it almost £1m last year alone.

In 2015, the Thomas Clarkson Academy, in Wisbech, fell below the government's floor standard for GCSE results for the third year in a row, and three months ago it was declared 'inadequate' by Ofsted.

The 2014-15 accounts of its sponsor, the Brooke Weston Trust, showed the deficit had risen from £661,000 the previous year.

The trust blamed it on 'significant increases in the cost of supply teachers as a result of the shortage of full-time teaching staff in the local area', and 'high buildings maintenance costs' under its PFI agreement.

A spokesman said: 'We have put in place a recovery plan for our budget deficit which is progressing well and year-on-year debt levels are reducing.

'The Education Funding Agency in its latest inspection has praised the financial management of the trust as robust.'

She said it was using retention packages to try to stabilise staffing numbers, and added that the school should break even in 2017-18.

The PFI deal to rebuild the school was signed by Cambridgeshire County Council (CCC) before it joined Brooke Weston, and ties the school in to paying for services including maintenance of premises and IT equipment, cleaning and 'the provision of certain utilities'.

The deal is due to run until 2037, but a spokesman said: 'It is an issue we have inherited and we are working with the local authority on this.

'As a trust we support the ongoing efforts by CCC and local politicians to revisit the terms of the PFI contract.'